The invention relates to an apparatus for gathering signatures along a conveying section of a circulating conveyor, provided with successively spaced apart pushers that are attached to a traction mechanism and are moved past delivery stations which are arranged along the conveying section. In the process, the signatures are supplied by the delivery stations, operating at approximately the same speed as the circulating conveyor, via a downward pointing, slanted feeding path to the conveyor.
Apparatuses of the aforementioned type are used, for example, for transporting signatures separated by feeders into the gathering channel of so-called gathering machines for perfect binding systems used in the graphics industry. Several delivery stations are arranged along the approximately horizontally extending gathering channel, which advance the signatures from a feeder into the gathering channel. A conveying device in the form of pushers that are attached to a circulating traction mechanism is provided in the gathering channel. The pushers push the stack of signatures gathered during the transport through the gathering channel. The signatures, supplied by the delivery stations, are stacked precisely one above the other to form complete stacks of gathered signatures since a later alignment of a completed signature stack is not reliably possible.
An apparatus of the aforementioned type is disclosed, for example, in German patent document DE 196 16 047. The signatures separated by the feeder are supplied with synchronous timing to the intake area of the delivery station, are transported by this delivery station to the gathering channel, and are deposited at a location where the stack of signatures is formed. The delivery station comprises respectively at least one driven upper and one lower belt section, between which the signatures are clamped in and conveyed. The conveying path takes the form of a straight section that is inclined relative to the gathering channel.
One disadvantage of the above arrangement relates to the curved areas of transition in the movement path for the signatures, at the intake and discharge of the conveying path. Signatures normally have a fold along the longitudinal and/or transverse edges, resulting in a reinforced area for the signatures. If a signature is subject to excessive bending stresses along the conveying path, the existing stiffness in the region of the longitudinal fold on the signature results in leaving traces of the bending which reduce the quality of the final product. In the case of signatures with only one longitudinal fold, the additional danger exists that the loosely fitted together signature components are displaced relative to each other. This disadvantage could be avoided by having a smaller inclination angle for the conveying path, but this would unfavorably affect the length of a delivery station which is not desirable for an apparatus having a plurality of delivery stations. A further disadvantage results from the contact rollers, which are spring-loaded and press the upper belt section against the lower belt section, thereby exerting high Hertzian stresses onto the print products. In particular with freshly imprinted signatures, the printing ink leaves impressions on the contacting sheet.